Additional information:

Foothill Yellow-legged Frog

Rana boylii

What do they look like?

The backs of foothill yellow-legged frogs are colored like the ground, so they can be almost black, dark brown, reddish brown, gray, olive, or greenish with spots and speckles. Some have a light spot within a dark area on their upper eyelid. Their underside is white or light yellow, and more yellow at the back of the body and back legs. They have a wide, pointy head. The bones between their knees and ankles are extra long, about half the length of the body. Their back feet are short and completely webbed. Foothill yellow-legged frogs are 3.8 to 8.1 cm long. Females are bigger than males, and they are 20 to 25 mm longer. ("Amphibians of Western North America", 1951; "Handbook of Frogs and Toads of the United States and Canada", 1995; Ashton, 1997; Leonard, et al., 1993; Stebbins, 2003)

What kind of habitat do they need?

Foothill yellow-legged frogs are almost always in the water. They live in streams, springs, and freshwater lakes, and prefer creeks with rocky bottoms. They usually live in gently flowing water. They prefer to lay eggs in creeks or streams with water that flows softly. Adults spend most of their time sitting on rocks in the stream or nearby on the banks. If they are startled, they immediately leap into the water and quickly swim to the bottom. In clear water, they take shelter under overhanging rocks. In streams with muddy bottoms, they stir up the silt on the bottom and hide in the mud. They live at sea level and anywhere up to 2,040 m in elevation. ("Amphibians of Western North America", 1951; "Handbook of Frogs and Toads of the United States and Canada", 1995; Leonard, et al., 1993)

How long do they live?

Scientists haven't determined the lifespan of foothill yellow-legged frogs. They might be able to live for 12 years or longer like their close relatives. ("AmphibiaWeb", 2010; Ashton, 1997)

There are many threats to how long foothill yellow-legged frogs live. They can be eaten by predators or infected with parasitic helminth worms. When it's dry, they are more likely to come on land. This means they are more likely to get eaten or have their eggs dry out. Flooding can make their eggs come off the rock they're stuck to, so they are less likely to survive. They are also affected by habitat loss, pesticides, new fish species, and competition with American bullfrogs. ("AmphibiaWeb", 2010; "California Reptiles and Amphibians", 2010; Ashton, 1997)

Range lifespanStatus: wild

3 (high) years

How do they behave?

Foothill yellow-legged frogs are typically active during the day, but they are very shy. They bask in the sun on rocks or along the shore, but quickly jump into the water if they get frightened. They can leap a long distance if their hiding place is hard to get to. They usually stay in the same spot, except that they will travel hundreds of meters to breeding sites. In warmer climates, they are active year-round. In colder climates, they hibernate in cold winters. Foothill yellow-legged frogs can change from a dark to lighter color within about half an hour. They give off an oily, garlicky smell when humans touch them. ("Amphibians of Western North America", 1951; "California Reptiles and Amphibians", 2010; "The Frog Book", 1913; Leonard, et al., 1993)

Home Range

Scientists don't know the size of the territory where foothill yellow-legged frogs usually live and travel. ("AmphibiaWeb", 2010)

How do they communicate with each other?

Like most other frogs, foothill yellow-legged frogs have a pair of small organs they use to make noise called vocal sacs. Their call is faint and not heard very often. In the mating season, they actually make most of their calls underwater because the stream makes it really noisy above the water. Foothill yellow-legged frogs make low-pitched and raspy sounds that are croaks, grunts or oinks. ("Amphibians of Western North America", 1951; "California Reptiles and Amphibians", 2010)

What roles do they have in the ecosystem?

Foothill yellow-legged frogs reduce the numbers of insects that they eat. They are a food source for many predators. Tadpoles limit how much algae grows because they eat so much of it. They are sensitive to pollution and other changes in their environment, so they can serve as an early warning about problems in their environment. Foothill yellow-legged frogs get different kinds of parasitic worms in their bodies. (Ashton, 1997; Chanson and Boucher, 2004; Leonard, et al., 1993)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

helminth woms

Do they cause problems?

There are no known negative impacts of foothill yellow-legged frogs on humans.

How do they interact with us?

Like most amphibians, foothill yellow-legged frogs are sensitive to problems in their environment. This means they are an excellent species to warn conservationists about problems in their habitat. This is because their skin allows pollutants to get inside their bodies. Foothill yellow-legged frogs also eat a lot of insects, and some of these are pests to humans. (Ashton, 1997; Chanson and Boucher, 2004)

Are they endangered?

Foothill yellow-legged frogs are listed as "Near Threatened" by the IUCN Red List. They are also listed as a California Species of Special Concern, according to the California Department of Fish and Game. They are affected by erosion, competition with American bullfrogs, loss of habitat, pesticides, logging, and mining. They are sensitive to changes in stream flow, water temperature, and the amount of sediment on the stream bottom. Some groups of them live in protected lands like national forests, parks, and land owned by conservation organizations. ("AmphibiaWeb", 2010; Fellers, 2010)